Electromagnetic square wave producing device



Dec. 18, 1962 A. E. FEINBERG 3,069,597

ELECTROMAGNETIC SQUARE WAVE PRODUCING DEVICE Filed Nov. 14, 1952 UnitedStates Patent 3,069,597 ELECTROMAGNETIC SQUARE WAVE PRODUCING DEVICEAlbert E. Feinberg, Chicago, Ill., assignor to Advance Transformer Co.,Chicago, 11]., a corporation of Illinois Filed Nov. 14, 1952, Ser. No.320,470 18 Claims. (Cl. 315--254) This invention relates generally totransformers and more particularly is concerned with a transformer ofthe character which When energized will produce .a substantially squareor clipped wave.

In the electrical lighting industry, high leakage reactance transformersare used to provide the necessary ballast in the use of gaseousdischarge devices such as fluorescent lamps, gaseous discharge tubes andthe like. It is required at times that a device in a circuit drawleading current. Under such circumstances, the transformer must provide,in addition to the high leakage reactance between the primary and thesecondary serving the leading gaseous discharge device, means to produceadditionall leakage react-ance at a point in the magnetic circuit incommon with both the primary and the leading secondary windings in orderto prevent saturation in the magnetic core. In the case of a simpletransformer for use with a single gaseous discharge device, this maytake the form of a non-magnetic gap at the end of the common magneticleg. This type of structure is also found advantageous in the case oflagging secondaries, but the likelihood of saturation .is not as great.

For example, in a shell type of transformer in which there is arectangular frame-like portion and a central longitudinal winding leghaving the winding disposed thereon, the two windings are separated by amagnetic shunt including air gaps, and the end of the winding legadjacent the secondary winding is also provided with an air gap. Thisproduces leakage reactance which is common to both the primary and thesecondary magnetizing fluxes. The construction as described preventssaturation in the core in the vicinity of the secondary Winding, whichis an undesirable characteristic of secondaries drawing leading current.

Mechanically, it is practically necessary that there be at least a verysmall bridging projection or protuberance on one or the other .of thejuxtaposed faces of the gap. This protuberance is needed for support andto prevent the chattering .or buzzing which may be caused by suchstructures. It has been found, however, that such structures, whileproviding current that is fairly sinusoidal, nevertheless cause anundesirable type of distortion characterized by a very sharp peak ofhigh amplitude superimposed on the resulting voltage wave. Two importantdisadvantages arise by virtue of this peak. In the first place, thesharp peak is tov some extent reflected in the current wave anddecreases lighting efficiency. In the second place, in the type ofgaseous discharge device which is required to be preheated beforeignition, such peaking of the voltage Wave will give rise to preignition, Under these circumstances, the filaments of such devices willbe bombarded by heavy ions during the time that their emitting facultiesare being built up, thereby shortening the life of such filaments.

I believe that the peaking is caused by a sudden increase in thepermeability of the small bridging connection or protuberance at the topof the voltage Wave giving rise to a surge or sudden increase in therate of change of flux. The voltage in a device of this kind lags theinstantaneous magnetic flux and the magnetizing current by 90 and isproportional to the rate of change of flux. Thus when the flux wavepasses through zero, the voltage is a maximum, i.e., reaches its peak.Likewise, when ice the flux wave is at a maximum, the voltage is zero.In a constricted flux path such as this small bridging projection orprotuberance, the permeability of the area will be large when the fluxis near zero (and the voltage maximum) and the permeability will droppractically to that of the surrounding air space due to its saturationwhen the flux increases at zero voltage. Now, as the flux decreasestoward zero, the permeability of the restricted area will continue toincrease until it will be very great near zero flux. At this point theflux will suddenly increase rapidly in the opposite direction until theconstricted area is once more saturated and the reluctance of that pathapproaches that of the air space surrounding this area. As the voltagedecreases from that point onward, the flux will continue to increase butat a slower rate. Obviously then, this would cause the peak at the crestof the volt-age wave, because the flux rate of change at the zero pointsuddenly increases.

This invention, therefore, has as a principal object thereof theelimination of the peaked voltage wave from the electromagneticstructure of character described 7 wherein the secondary may be carryinga leading current.

A further object of the invention is the provision of a novelelectromagnetic device which will produce a generally square currentwave in the secondary thereof, whereby when used with gaseous dischargedevices providing illumination, greater lighting efficiency will beobtained.

Still another object of the invention is to provide a transformer of thecharacter described in which the magnetic high leakage reactance shuntbetween the primary and secondary windings is provided with highlyconstricted bridging portions whereby to offset and overcome thetendency of the leading secondary to produce peaked crest current waves.

A still further object of the invention is to provide a transformerwhich will produce a generally square or clipped voltage wave and iscapable of delivering a current of like wave shape to a load.

Many other objects will occur to those skilled in the art to which theinvention appertains, but all within the purview and scope of theinvention. For the purpose of complying with the patent statutes 1 haveillustrated preferred embodiments of the invention which, whenconsidered in connection with the description will clearly demonstratethe advance that I have made in the arts and sciences.

In the drawings:

FIG. 1 is semi-diagrammatic view generally in section showing theconstruction of a transformer or the like of the kind to which theinvention may be applied, illustrating prior constructions.

FIG. 2 is a schematic electrical diagram of a circuit utilizing thedevice of FIG. 1 for the ignition and operation of a gaseous dischargetube for lighting purposes.

FIG. 3 is a fragmentary view of the end of a device of the type shown inFIG. 1 but having a modified form of the prior construction.

FIG. 4 is a diagrammatic representation of the voltage wave produced inthe secondary of the device of FIG. 1 or FIG. 3, showing the peakedcrests.

FIG. 5 is a semi-diagrammatic view generally in section similar to thatof FIG. 1 but showing the construction of the invention.

FIGS. 6, 7 and 8 are fragmentary views of the center of a transformer orother magnetic device similar to that of FIG. 5 but showing modifiedforms of the invention.

FIGS. 9 and 10 are diagrammatic representations of voltage wavesproduced in the secondaries of the devices of FIGS. 5 to 8 inclusive andshowing the manner in which the crests of the waves are flattenedbecause of the invention.

In FIG. 1 there is illustrated a transformer of the general type withwhich we are concerned. Although illustrated with only one secondarywinding, it is to be understood =that same may have more than one. Thesewindings may be of any character such as for example, lagging windings,split windings, etc.

The phenomena with which we are here concerned arise by virtue of theexistence of an end gap. Such end gaps are especially useful inpreventing saturation which might occur in the vicinity of the secondarywinding in the event the secondary winding was designed to carry aleading current. However, due to the improvement in wave shape, undercertain circumstances, the secondary may carry lagging current. Theinvention is applicable to both types of secondaries.

There is shown a transformer 2t having a shell-like outer core 21 havingbridging ends 22 and The transformer is formed of two windings, aprimary P and a secondary both of which are mounted upon a centralwinding leg 24 and are spaced apart sufficient to clear the magneticshunt 26 between the windings. The left hand end of the winding leg 24matingiy engages at in the bridging end. 22 with good magnetic contactand the right hand end of the winding leg 24 has been foreshortened toprovide a space or air gap 27 at that point. There is a very smallbridging projection 28 in the center of the end face of the winding legwhich engages the opposite face of the gap 27 so as to support thecentral winding leg 24 in proper position within the shell core 21.

In the fabrication of this transformer it) it is usual that the centerwinding leg 24 be punched out of the large plates forming thelaminations of the core 21 so that there is exact fit at the 'uncture25. The gaps 2'7 and St) in the shunt are then shaved. The windings Pand S are pro-wound, slipped over the ends of the winding leg 24 and theassembled winding leg is pressed home into the core. The connections aretaken out of the cannister in which the transformer is disposed, withperhaps condensers and other electrical elements suitably connected, andthe entire device is potted, i.e., covered with pitch, and sealed.

Returning now to the construction of the transformer 2%), the magneticshunt may be formed of extensions from the sides of the core 20 whichface the sides of the winding leg, or, as in the case illustrated inFIG. 1, the sides of the core and the winding leg may be provided withshort extensions 32 and 353 which are spaced apart sumcient to providethe gaps 30.

In FIG. 3, instead of the protuberance 28, the transformer 26 may havethe central winding leg seated in a shallow recess formed in thebridging end, the recess in turn having a portion narrower than thewidth of the winding leg so that there are formed corner support notches34 for the winding leg 2-4. The effect is the same as in FIG. 1.

Referring now to FIG. 2, there is shown the diagram of the circuit ofthe transformers of FIGS. 1 and 2. This, together with the transformerform no part of the invention but merely illustrate the difliculty whichthe invention overcomes. The circuit shows the transformer 29 beingdesignated in the conventional manner and having the primary P and thesecondary S connected end to end at the juncture 40. The primary P isconnected across the line which is indicated by the terminals 41 and 42.The core 26 and the shunt 26 are designated by groups of lines in theconventional manner. In this instance the secondary S is intended todraw a leading current. There is shown a gaseous discharge device in theform of a fluorescent lighting tube 43 connected across both of thewindings P and S by the left hand lead 44 which extends to the terminal42 and the right hand lead 45 which extends to the right hand end of thesecondary S and has a condenser C in series therein. This is anauto-transformer connection. The operation of the device is well knownand consists of the ignition of the lamp 43 by virtue of the opencircuit voltage developed across both windings followed by theprotection of relatively large reactance whereby to limit the flow ofcurrent in the lamp. The circuit may be varied by the addition of otherwindings as previously mentioned herein and instead of the instant-startlamp illustrated, a pre-heat type of fluorescent lamp may be used.

In FIG. 4 I have shown the positive and negative cycles of a voltagewave which results from the phenomena heretofore discussed. The generalconfiguration of the wave is that of a sine wave as indicated at 47 but,it will be seen that the great increase in rate of change of flux whichoccurs when the voltage is a maximum results in peaks 48 superimposedupon the sine wave 47. It has been found desirable to produce a currentin the. lamp 43 which is fairly flat topped in order to achieve maximumbrilliance during the greatest part of the cycle. Obviously the currentwave which would result by reason of the voltage wave of FIG. 4- wouldlikewise be peaked and certainly not flat topped. Furthermore, aspointed out the peaks which are caused by the construction heretoforeused also may produce pro-ignition in the pre-heat type of fluorescentlamp.

The invention as previously stated has as its principal object theelimination of the peak and the production instead of a relativelyfiat-topped wave. This is done by the elimination of the protuberance 23at the right hand end of the win-ding leg 24 such that the great rate ofchange of flux is impossible. Furthermore, by providing such aprotuberance at the magnetic shunt 26, there is provided a by-passing offlux at the magnetic shunt 26 which will automatically decrease thevoltage developed in the secondary at the point of maximum voltage. Thisresults in just the opposite of the phenomena described so that insteadof the peak as shown in FIG. 4 there is a dip as shown at 49 in FIG. 9.By suitable design the dip may be modified to provide a relatively flattopped wave which is illustrated in FIG. 10.

I believe that this is caused by the same general principles which giverise to the peaking. The permeability of the protuberance at the shunt26 is increased as the voltage increases, while the flux approacheszero, so that the flux tends to pass through these protuberances insteadof through the end gap 27. This compresses the flux wave so that therate of change as the flux wave passes through zero (point of maximumvoltage) is considerably reduced. Obviously, with voltage beingproportional to rate of change of flux, there will be no sharp peak atthe voltage crest.

FIGS. 5, 6, 7 and 8 illustrate the forms Which the invention may take.Thus, in PEG. 5 there is shown a transformer 50 whose construction issimilar to that of the transformer 26 in FIG. 1 with certain importantexceptions. The gap 27 in transformer 50 is unobstructed by reason ofthe elimination of the protuberance 2S and the winding leg 24 issupported by means of a protuberance 51 carried by each of theextensions 33 of the magnetic shunt 26. In order to eliminate end-wiseplay of the winding leg 24 the gaps 3d are slanted downwardly andtowards the right, so that any tendency of the winding leg to pull awayfrom the connection 25 will result merely in a tight wedging engagementof the extensions 32 with the protuberances 51.

In FIG. 6 there is shown a modified form of the invention. In thisinstance transformer 6t? is provided with inwardly extending parts 53which stop just short of the central winding leg 24. The central windingleg 24 is also provided with outwardly extending parts 54 which extendto just short of the. inner edges of the core 21. The vertical facingsurfaces of the extensions 53 and 54 are also spaced apart so that arelatively long air gap 55 is formed. This provides a large gap area,especially needed in the cases where S is to carry a lagging current.The facing vwith a relatively peaked wave.

7 surfaces of the extension 53 are each provided with smallprotuberances 56 whose purpose is the same as the protuberance 51 ofFIG. 5. In FIGS. 7 and 8 no provision is shown to prevent end wisemovement of the central winding leg 24 and it is presumed that someexpedient 'Will be used to counter this movement during operation of thetransformer.

For example, the end gaps 27 may be filled with some non-magneticsubstance such as fibre, paper or the like. In the case of thetransformer 70 the outwardly extending portions 32 are each providedwith a pair of protuberances 72 to produce the necessary effect. In thecase of the transformer 80 the inwardly extending portions 33 are eachprovided with a single protuberance 82 also for the purpose set forthabove. Obviously in each of the forms of FIGS. 5 through 8 there may beone or more small protuberances used if desired, depending upon theresults expected.

The wave shape which is produced in the current of the secondary S as aresult of these constructions has been found to produce considerablybetter illumination than The ratio of peak to R.M.S. voltage can be madeless than 1.414 with excellent results.

The constructional details of transformer shown in FIG. 1 and thecircuit thereof shown in FIG. 2 are known in the prior art. Thedimensions of the examples of FIGS. 5 to 8 are of the same generalproportion with the protuberances 51, 56, 72 and 82 of a practical sizeto maintain the gap spacing and firmly hold the respective winding legs24- in place.

While I have shown and described specific examples of the invention asused in connection with gaseous discharge devices, it is pointed outthat the device has much broader application. 'In many cases in which asquare wave is desired, and where from the type of load electromagneticmeans are appropriate, the invention may be applied. Likewise theconstructions which have been shown and described by way of examples arecapable of wide variation. The device may for example be constructed ofL-shaped laminations arranged one opposite the other in which case thereis no central winding leg. In this case, the windings are usually eachsplit into halves and placed on opposite legs of the respective Us Theshunt between the secondary and the rest of the device may be a stack oflaminations added, and may have only one gap instead of two. Similarvariations of structure are obviously possible.

In conclusion, it is desired to emphasize that the theory of operationof the invention has not been set forth by way of limitation but onlyfor clarification. I desire to cover all the modifications of theinvention construction as described, irrespective of the theory ofoperation, except of course as limited by the claims appended hereto.

What it is desired to claim by Letters Patent of the United States, is:

1. An electromagnetic device serving at least one gaseous dischargedevice and adapted to ignite and thereafter'regulate the operation ofthe same from a relatively low voltage source of A.C. voltage, includingat least a primary winding and a secondary winding, the primary windingbeing connected with the source to be energized thereby, and physicallyseparated from the secondary winding, the windings being connected intransformer relationship, and the gaseous discharge device beingconnected to the secondary so that the secondary current will flowthrough the discharge device, a shell-like core mounting said windingsand including a central wind ing leg, the secondary winding beingpositioned at an end of the said winding leg within the shell-like core,the core including a bridging end member, the end of the winding legmounting said secondary winding being slightly spaced from the bridgingmember and totally free therefrom to provide an end gap, a magneticshunt separating the secondary winding from the remainder of thetransformer and including an air gap on opposite sides of the centralwinding leg, at least one minute protuberance bridging each of thelast-mentioned gaps for maintaining the spacing of the gaps and servingas a flux bypass path at maximum open circuit voltage, whereby toflatten the voltage crest.

2. An electromagnetic device serving at least one gaseous dischargedevice and adapted to ignite and thereafter regulate the operation ofthe same from a relatively low voltage source of AC. voltage, includingat least a primary winding and a secondary winding, the primary windingbeing connected with the source to be energized thereby, and physicallyseparated from the secondary winding, the windings being connected intransformer relationship, and the gaseous discharge device beingconnected to the secondary so that the secondary current will flowthrough the discharge device, a shelllike core mounting said windingsand including a central winding leg, the secondary winding beingpositioned at an end of the said winding leg within the shell-like core,the core including a bridging end member, the end of the winding legmounting said secondary Winding being slightly spaced from the bridgingmember and totally free therefrom to provide an end gap, a magneticshunt separating the secondary winding from the remainder of thetransformer and including an air gap on opposite sides of the centralwinding leg, at least one minute protuberance bridging each of thelast-mentioned gaps for maintaining the spacing of the gaps and servingas a flux by-pass path at maximum open circuit voltage, whereby toflatten the voltage crest, the said last mentioned gaps slantinginwardly toward the winding leg and end of the transformer having saidend gap whereby any endwise movement of the central winding leg towardthe said eng gap will be resisted by the said protuberances.

3. An electromagnetic device serving at least one gaseous dischargedevice and adapted to ignite and thereafter regulate the operation ofthe same from a relatively low voltage source of A.C. voltage, includingat least a primary Winding and a secondary winding, the primary windingbeing connected with the source to be energized thereby, and physicallyseparated from the secondary winding, the windings being connected intransformer relationship, and the gaseous discharge device beingconnected to the secondary so that the secondary current will flowthrough the discharge device, a shell-like core mounting said windingsand including a central winding leg, the secondary winding beingpositioned at an end of the said winding leg within the shell-like core,the core including a bridging end member, the end of the winding legmounting said secondary winding being slightly spaced from the bridgingmember and totally free therefrom to provide an end gap, a magneticshunt separating the secondary winding from the remainder of thetransformer and including an air gap on opposite sides of the centralwinding leg, at least one minute protuberance bridging each of thelast-mentioned gaps for maintaining the spacing of the gaps and servingas a flux by-pass path at maximum open circuit voltage, whereby toflatten the voltage crest, there being an inward extension on each ofthe core sides adjacent the secondary winding, and an outward extensionon each side of the central winding leg approaching but not meeting thesaid inward extensions whereby to form said shunt and said lastmentioned gaps.

4. An electromagnetic device serving at least one gaseous dischargedevice and adapted to ignite and thereafter regulate the operation ofthe same from a relatively low voltage source of AC. voltage, includingat least a primary winding and a secondary winding, the primary windingbeing connected with the source to be energized thereby, and physicallyseparated from the secondary winding, the windings being connected intransformer relationship, and the gaseous discharge device beingconnected to the secondary so that the secondary current will flowthrough the discharge device, a shell-like core mounting said windingsand including a central winding leg, the secondary winding beingpositioned at an end of the said winding leg within the shell-like core,the core including a bridging end member, the end of the winding legmounting said secondary winding being slightly spaced from the bridgingmember and totally free therefrom to provide an end gap, a magneticshunt separating the secondary Winding from the remainder of thetransformer and including an air gap on opposite sides of the centralwinding leg, at least one minute protuberance bridging each of thelastmentioned gaps for maintaining the spacing of the gaps and servingas a flux by-pass path at maximum open circuit voltage, whereby toflatten the voltage crest, there being an inward extension on each ofthe core sides adjacent the secondary winding, and an outward extensionon each side of the central winding leg approaching but not meeting thesaid inward extensions whereby to form said shunt and said lastmentioned gaps, said protuberances being integral with a pair ofextensions.

5. An electromagnetic device serving at least one gaseous dischargedevice and adapted to ignite and thereafter regulate the operation ofthe same from a relatively low voltage source of A.C. voltage, includingat least a primary winding and a secondary winding, the primary windingbeing connected with the source to be energized thereby, and physicallyseparated from the secondary winding, the windings being connected intransformer relationship, and the gaseous discharge device beingconnected to the secondary so that the secondary current will flowthrough the discharge device, a shell-like core mounting said windingsand including a central winding leg, the secondary winding beingpositioned at an end of the said winding leg within the shell-like core,the core including a bridging end member, the end of the winding legmounting said secondary winding being slightly spaced from the bridgingmember and totally free therefrom to provide an end gap, a magneticshunt separating the secondary winding from the remainder of thetransformer and including an air gap on opposite sides of the centralwinding leg, at least one minute protuberance bridging each of thelast-mentioned gaps for maintaining the spacing of the gaps and servingas a flux by-pass path at maximum open circuit voltage, whereby toflatten the voltage crest, there being an inward extension on each ofthe core sides adjacent the secondary winding, and an outward extensionon each side of the central winding leg approaching but not meeting thesaid inward extensions whereby to form said shunt and said lastmentioned gaps with adjacent extensions being generally rectangular inconfiguration and having facing edges perpendicular to the centralwinding leg.

6. An electromagnetic device serving at least one gaseous dischargedevice and adapted to ignite and thereafter regulate the operation ofthe same from a relatively low voltage source of AC. voltage, includingat least a primary winding and a secondary winding, the primary windingbeing connected with the source to be energized thereby, and physicallyseparated from the secondary winding, the windings being connected intransformer relationship, and the gaseous discharge device beingconnected to the secondary so that the secondary current will flowthrough the discharge device, a shell-like core mounting said windingsand including a central winding leg, the secondary winding beingpositioned at an end of the said winding leg within the shell-like core,the core including a bridging end member, the end of the winding legmounting said secondary winding being slightly spaced from the bridgingmember and totally free therefrom to provide an end gap, a magneticshunt separating the secondary winding from the remainder of thetransformer and including an air gap on opposite sides of the centralwinding leg, at least one minute protuberance bridging each of thelast-mentioned gaps for maintaining the spacing of the gaps and servingas a flux by-pass path at maximum open circuit voltage, whereby toflatten the voltage crest, there being an inward extension on each ofthe core sides adjacent the secondary winding, and an outward extensionon each side of the central winding leg approaching but not meeting thesaid inward extensions whereby to form said shunt and said lastmentioned gaps with adjacent extensions being generally rectangular inconfiguration and having facing edges perpendicular to the centralwinding leg with the protuberances between said facing edges.

7. An electromagnetic device serving at least one gaseous dischargedevice and adapted to ignite and thereafter regulate the operation ofthe same from a relatively low voltage source of AC. voltage, includingat least a primary winding and a secondary winding, the primary windingbeing connected with the source to be energized thereby, and physicallyseparated from the secondary winding, the windings being connected intransformer relationship, and the gaseous discharge device being c011-nected to the secondary so that the secondary current will flow throughthe discharge device, a shell-like core mounting said windings andincluding a central winding leg, the secondary winding being positionedat an end of the said winding leg within the shell-like core, the coreincluding a bridging end member, the end of the winding leg mountingsaid secondary winding being slightly spaced from the bridging memberand totally free therefrom to provide an end gap, a magnetic shuntseparating the secondary winding from the remainder of the transformerand including an air gap on opposite sides of the central winding leg,at least one minute protuberance bridging each of the last-mentionedgaps for maintaining the spacing of the gaps and serving as a fluxby-pass path at maxi mum open circuit voltage, whereby to flatten thevoltage crest, there being an inward extension on each of the core sidesadjacent the secondary winding, and an outward extension on each side ofthe central winding leg approaching but not meeting the said inwardextensions whereby to form said shunt and said last mentioned gaps withadjacent extensions being generally rectan ular in configuration andhaving facing edges perpendicular to the central winding leg and havingends terminating short of the core sides and central winding legrespectively whereby the gap formed thereby is of relatively greatlength and hence large area.

8. An electromagnetic device of the character described which isdesigned to provide substantially square wave of voltage to a gaseousdischarge device which comprises, a rectangular shell core, a centralwinding leg matingly seated in the core and having an end thereofterminated just short of the inner face of an end of the core and nottouching the same whereby to provide an end gap, a magnetic shunt spacedfrom the end gap to provide a winding window and extending between thesides of the shell core and the winding leg and including at least anon-magnetic gap, a source of AC. voltage, a secondary winding disposedin the window, a primary winding on the winding leg opposite saidsecondary winding and being connected across said source to be energizedthereby, a transformer connection between the windings whereby thesecondary will provide a current when energized by the primary, agaseous discharge device connected with the secondary winding, and asmall bridging head of magnetically conducting material rigidly engagedin said non-magnetic gap of said shunt.

9. A device as described in claim 8 in which the windings are connectedin auto-transformer connection and the gaseous discharge device isconnected across both windings.

10. A device as described in claim 8 in which the windings are connectedin auto-transformer connection and the gaseous discharge device isconnected across both windings and there is a condenser in seriestherewith.

11. A transformer providing a flattened voltage wave to a load,comprising a primary winding and a secondary winding connected intransformer relationship, a magnetic core having the windings mountedthereon, a common flux path for the flux of said windings in the corehaving an air gap therein to limit the flux density in the vicinity ofthe said secondary winding, and a saturable shunt between the windings,said shunt being saturated throughout substantially all of the outputvoltage wave of said transformer, except at the peak of said wave, andhaving relatively high permeability at said peak.

12. A transformer providing a flattened voltage wave to a. load,comprising a primary winding and a secondary winding connected intransformer relationship, a magnetic core having the winding mountedthereon, a common flux path for the fiux of said windings in the corehaving an air gap therein to limit the flux density in the vicinity ofthe said secondary winding, and a saturable shunt between the windingsfor diverting the primary magnetic flux during operation or" thetransformer, said shunt including a highly constricted portioncompletely saturated at zero open circuit secondary voltage, and havingmaximum permeability at peak open circuit secondary voltage.

13. A transformer providing a flattened signal to a load, comprising amagnetic core, a primary winding connected to an AC. source, a secondarywinding in transformer relationship to the primary winding, the windingsmounted on said core with a common flux path, the load being connectedwith at least the secondary winding, 21 non-magnetic gap in the core andin the said common flux path, a shunt between the windings, and meansrendering the shunt highly saturable throughout the entire cycle of theoutput voltage except at peak amplitude.

14. A transformer providing a flattened signal to a load, comprising amagnetic core, a primary winding connected to an AC. source, a secondarywinding in transformer relationship to the primary winding, the windingsmounted on said core with a common flux path, the load being connectedwith at least the secondary winding, a non-magnetic gap in the core andin the said common flux path, a shunt between the windings, at least apart of the shunt having cross-sectional area very small relative to theremainder of the flux paths of the said core whereby said shunt issaturable during operation except at peak open circuit voltage.

15. A transformer providing a flattened signal to a load, comprising amagnetic core, a primary winding connected to an A.C. source, asecondary winding in transformer relationship to the primary winding,the windings mounted on said core with a common flux path, the loadbeing connected with at least the secondary winding, a non-magnetic gapin the core and in the said common flux path, a shunt between thewindings, at least a part of the shunt having cross-sectional area verysmall relative to the remainder of the flux paths of the said corewhereby said shunt is saturable during operation except at peak opencircuit voltage, at least a part of the said shunt being of a magneticmaterial having a relatively low saturable flux density.

16. A transformer providing a flattened signal to a load, comprising amagnetic core, a primary winding connected to an AC. source, a secondarywinding in transformer relationship to the primary winding, the windingsmounted on said core with a common flux path, the load being connectedwith at least the secondary winding, a non-magnetic gap in the core andin the said common flux path, a shunt between the windings, at least apart of the shunt having cross-sectional area very small relative to theremainder of the flux paths of the said core whereby said shunt issaturable during operation except at peak open circuit voltage, saidshunt including at least a non-magnetic gap having a small bridgingprotuberance therein, whereby the protuberance is saturated and ofsubstantially the permeability of the remainder of the gap except atpeak open circuit voltage.

17. A high reactance transformer comprising a magnetic core having awinding leg member and a multileg yoke member, one end leg of said yokemember abutting one end of said Winding leg member and the other end legof said yoke member defining a series air gap with the other end of saidwinding leg member, a primary winding and a secondary winding in spacedrelation on said Winding leg member, said yoke member having a leakageleg extending intermediate said primary and secondary winding towardsaid winding leg member and defining a shunt air gap with said windingleg member, and a magnetic bridge across the shunt air gap between saidleakage leg and said winding leg, said bridge maintaining the spacingand position of both said series and shunt air gaps and reducing theopen circuit peak voltage of said secondary winding.

18. A high reactance transformer of claim 17 wherein the magnetic bridgecomprises a portion of the leakage leg abutting said winding leg member.

References Cited in the file of this patent UNITED STATES PATENTS2,496,981 Boucher Feb. 7, 1950 2,562,693 Brooks July 31, 1951 2,683,243Feinberg July 6, 19 54

